Which of the following could be considered the most recent common ancestor of living tetrapods?a. a sturdy-finned, shallow-water lobe-fin whose appendages had skeletal supports similar to those of terrestrial vertebratesb. an armored, jawed placoderm with two pairs of appendagesc. an early ray-finned fish that developed bony skeletal supports in its paired finsd. a salamander that had legs supported by a bony skeleton but moved with the side-to-side bending typical of fishes